The automotive industry is increasingly using electrical systems to provide at least a portion of the propulsion power for automotive vehicles. These electrical systems typically use high voltage, which is generally defined as direct current (DC) voltage of at least 60 VDC or alternating current (AC) voltage of at least 30 VAC.
Protection against unintended access to high voltage may be provided is via a dedicated high-voltage interlock (HVIL) circuit, or a combination of dedicated loop and localized loops where deemed appropriate. A localized HVIL loop is used to protect one or more high voltage access points, but a subset of the total number of vehicle access points. Localized HVIL loops are used when that subset can have a different response to HVIL breach event, or when physical HVIL implementation can be more economically achieved. For example, localized HVIL could be used in a HV-based air conditioner, where the detected breech of HVIL might trigger a shutdown of only the air conditioning system. An HVIL circuit is a low-voltage circuit. The HVIL circuit typically includes a dedicated circuit loop that is routed to an associated access point, such as component covers or high-voltage connectors, which allow personnel access to high-voltage. The HVIL circuit loop is energized with a low-voltage signal and is configured to be open-circuited when its associated access point is breached. Whenever the HVIL circuit loop is open-circuited, indicating that the associated access point is breached, the HVIL circuit de-energizes the high-voltage to all of the components associated with the breached access point.